Kendall Jenner's sleep paralysis

The 21-year-old model admitted she has been left exhausted by the condition as she explained it to her older sister Kim Kardashian West, 36, on their reality TV show 'Keeping Up With The Kardashians'.

She said: "It's like you're asleep, and then in the middle of the night...basically, your mind wakes up but your body is still asleep. You wake up, and nothing can move.

"It's the scariest thing in the entire world, you're freaking out because all you want to do is be able to move, so you're laying there, trying to move, trying to relax."

Kim was shocked to hear of her sister's condition and said in a confessional to the cameras: "I thought I was having anxiety, this is like, so much scarier. I've never heard of sleep paralysis and I think it sounds like such a crazy experience."

Meanwhile, their sister Khloe Kardashian, 32, has revealed that Kendall got so drunk at her 21st birthday party last week that she forgot a prince gave her a Rolls Royce.

Khloe said: "We go outside and there's a guy with a Rolls Royce, we're like 'what's the gift, the guy or the Rolls?'

"And then the guy just hands her the keys to this car. We don't know who this guy is, he's some prince.

"I was like 'Is this a joke?' I think on my 21st birthday I got like a dinner and a purse or something.

"The next morning I asked her about it and she said, 'Oh my God I forgot I got a car!' That's how drunk she was."

The model's new car is the latest addition to her growing collection, which already includes a Range Rover and $100,000 Chevrolet.

Kendall's famous family hired out a private function room, which was decorated with large balloons emblazoned with her name, at Coach restaurant to kick off the festivities and all guests were told to wear floral headpieces at their seats in order to set the mood.

After polishing off their tasty meal, the party moved on to Delilah, where the model was presented with an "adorable" cake, which had a "throwback photo of her in a purple tutu" pasted on.

As well as the famous family, Kendall's best friend Hailey Baldwin, Cindy Crawford, Kate Mara, Melanie Griffith, Gabrielle Union, Paris Hilton and Jonathan Cheban were in attendance.

The bash also saw a surprise appearance from Kendall's half-sister Kim Kardashian West, who has kept a low profile since she was held at gunpoint in France last month and Kendall's ex Harry Styles was also spotted.